London: Britain's longest serving Indian-origin Labour MP Keith Vaz faces a possible investigation by the House of Commons standards watchdog after a newspaper claimed that he had paid for male prostitutes.

Vaz, 59, who is expected to announce his decision to step aside as chair of the influential Commons' Home Affairs Committee on Tuesday, is to be referred to the UK's Parliamentary Commissioner for Standards Kathryn Hudson by Conservative MP Andrew Bridgen.

Keith Vaz. AFP

"We need a full police and criminal investigation into Mr Vaz's affairs, I think we need the Parliamentary Standards investigation...at the end of the day I think Mr Vaz has historically and is now currently bringing Parliament into disrepute and I don't think he is a fit and proper person to be a Member of Parliament," Bridgen said.

Vaz, who is married and has two children, is alleged to have met two male prostitutes from eastern Europe at his London flat last month, according to Sunday Mirror.

He is alleged to have told the escorts to bring the party drug known as "poppers" and is also quoted as discussing the possibility of paying for cocaine at a future meeting, but added that he would not take the drug himself.

"It should be treated as a private matter. He is going to meet the Home Affairs Committee and discuss with them what his role will be in the future. I’m not sure what that decision will be but I leave it to him to decide on that," said Labour party leader Jeremy Corbyn, who appeared to indicate the party had no intention to take any further action against Vaz.

"Well, he hasn't committed any crime that I know of. As far as I'm aware it is a private matter, and I will obviously be talking to Keith," Corbyn told the Evening Standard when asked if he would want Vaz to remain within the party fold.

A Downing Street spokesperson said today that it was "up to him" if he feels his chairmanship of the Home Affairs Committee is still tenable.

While Vaz has indicated his decision to "step aside" from the role, a formal announcement on whether this is a temporary or permanent move is expected only tomorrow.

He is accused of meeting the escorts at least twice last month and is alleged to have told them that his name was Jim, adding that he was a washing-machine salesman.

A man linked to anti-diabetes charity Silver Star, launched by Vaz, unwittingly paid 300 pounds to the escorts, according to the Sunday Mirror.Sunday Mirror.

Malde Modhwadia, who has served as a trustee of the charity, said he was unaware of the payments or whether the charity had any involvement.

The UK's Charity Commission said it was aware of the report and would consider getting involved if it felt there was any impropriety.

In his only statement so far, Vaz has apologised to his family for "hurt and distress" caused, adding: "It is deeply disturbing that a national newspaper should have paid individuals to have acted in this way. I have referred these allegations to my solicitor Mark Stephens of Howard Kennedy who will consider them carefully and advise me accordingly.

"At this time I do not want there to be any distraction from the important work the Home Affairs Select Committee undertakes so well… I will of course inform committee members first of my plans when we meet on Tuesday.

"My decision has been based entirely on what is in the best interests of the committee which I have had the privilege of chairing for the last nine years."

Under Vaz’s chairmanship, the Home Affairs Committee recently concluded that soliciting by prostitutes should no longer be a crime.

Vaz had also opposed a UK government plan to outlaw "poppers" and ministers ultimately decided not to make their use illegal.

The Goa-born MP for Leicester East has served as Europe minister under former prime minister Tony Blair between 1999 and 2001. His sister, Valerie Vaz, is also an MP since the May 2010 general election.